1. Technical Field
This invention relates generally to diverse fields impacted by the nature of molecular interaction, including biology, chemistry, medicine and diagnostics. More particularly, this invention is directed to a miniaturized integrated system for analyzing airborne biological particles and microorganisms.
2. Description of Related Art
Obtaining accurate measurements of the particle and gas content in diverse environments including the earth""s atmosphere is important for monitoring and understanding such environments. Detection of biological warfare agents, collection of industrial pollutants in ambient air and fluids and sampling the same, collection of infectious or disease-causing organisms in closed and open spaces, as well as collection of radioactive particles or toxic vapors are just a few examples illustrating application of a system for analyzing biological particles and microorganisms.
The detection of low concentrations of aerosolized particles, i.e., particles suspended in air, generally requires that the particles be extracted from a large volume of air in order to capture a sufficient number of particles to exceed a detection threshold of a detection technique. For example, it is not uncommon to require the detection of aerosol concentrations of less than one hundred particles per liter of air. Typically immunoassay-type systems require approximately 100,000 organisms to achieve a successful detection. Obtaining this result from low concentrations can require particle extraction from over 1500 liters of air. Completion of this task in a timely manner (several minutes) requires that large volumes of air be processed.
Much effort has been expended in the past in the detection and classification of particles or aerosols in fluid streams. Impactors have been used for collecting aerosol particles for many decades. In the earliest embodiments, a stream of fluid containing the particles was accelerated toward an impactor plate. Due to their inertia, the particles hit the impactor plate and were collected there while the fluid was deflected to the side. With these types of impactors, only heavy particles were collected while particles below a certain xe2x80x9ccut sizexe2x80x9d were carried away by the fluid stream.
However, a significant cause of inaccuracy in such impactors results from the deposition of particles on surfaces of the impactor other than the intended collection surfaces. This phenomenon reduces the accuracy of measurement of total particle mass concentration and of the size-fractionation of particles, since such losses cannot be accurately estimated for aerosols having varying size, shape, or chemistry. Additionally, particles may either reenter the fluid stream or bounce from the impactor""s collection surface upon impact.
Another method for the detection and classification of particles is based on removing aerosolized particles from fluid streams by centrifugal force. This method is usually referred to as a xe2x80x9ccyclone.xe2x80x9d In accordance with this method, the aerosol is drawn into a cylindrical chamber so that the air makes one or more rotations inside before leaving the chamber through a tube at its center. Particles with sufficient inertia move centrifugally toward the inner wall.
A detection system associated with the cyclone principle of operation collects airborne particles from large volumes of air and concentrates the collected particles in a small volume of fluid. This fluid then can be inserted into a detection device such as an immunoassay cartridge to determine if a specific biological organism or agent is present. A schematic of such a system is shown in FIG. 1.
In the shown system, air is drawn into a liquid-impinging system 10 such as a wetted wall cyclone or other sample collector 12. As the air moves in a circular path, the water level rises, and particles impacting upon the surface of the sample collector 12 are captured in the fluid while the particle-free air exists out via the top of the jar. The fluid with captured particles is further transported for analysis by means of valves or pumps 14. Systems intended to detect harmful biological agents require the delivery of the sample fluid to an array of immunoassay cartridges so that multiple analyses may be performed. Typically, the sample collector provided with an impinger nozzle is located a substantial distance from a multiplicity of tickets, each of which typically carries only an array of immunoassay strips. To couple the collector 12 with the selected ticket, the latter is moved to a location to be connected to the collector 12 via a pump 14 and a system of valves providing sample flow into the strips of the connected ticket. Once the strips are filled, the ticket is again displaced a substantial distance toward a detector 22, which is configured to detect harmful agents. Upon completion of a positive detection, the remaining contents of the sample collector 12, if any, are drained. A large volume cleaning solution reservoir 18 is then coupled to the collector 12 and to the sample-solution conveying parts, such as, for example, the fluid transfer pump and coupling lines, to clean and prepare them for a subsequent test; once the cleaning stage is completed, the contaminated solution is accumulated in a large-volume waste basin 20.
Thus, the present technology requires that fluid from a single collection be transported a long distance to the detector. Before a new sample can be collected, analysis of the previous sample must be completed and the fluidics cleaned to prevent cross contamination. This process limits the maximum rate at which samples can be processed and amounts to a process that lasts about fifteen minutes.
Only after minimizing the possibility of cross-contamination, a new volume of the liquid is supplied from a collector supply 16 into the sample collector 12 to provide a trap for a new portion of particles entering the collector along with incoming air stream. To preserve tested samples for further consideration, a multiplicity of storage reservoirs 24 can be filled upon the completion of each test.
Thus, to summarize above, there are several significant disadvantages to this approach. First, transfer of the collected fluid to the detector is very complicated for multiple use systems. Second, between each analysis cycle the system must be purged to reduce cross contamination, requiring additional time and consumables. Third, the long fluid paths and complicated valve systems increase the likelihood of the system clogging due to environmental contaminants. Finally, in cold weather, significant power is required to prevent the fluids in the system from freezing.
It is, therefore, desirable to provide a simplified system for detecting aerosolized biological particles that requires fewer fluid-containing and fluid-conveying components and minimizes efforts directed to coupling these components for conducting a multiplicity of sequential tests.
To attain this, the present invention provides for a new configuration of a particle or sample collection and detection component, further referred to as a ticket, which includes, in addition to a cartridge provided with a row of immunoassay strips, a combination of an impinging nozzle, and sample reservoir. Optionally, a cleaning solution storage or reservoir can be an integral part of the inventive ticket. Thus, the inventive ticket is an integrated structural unit including a sample capturing and accumulating system, a cleaning system and a detecting system.
One of the advantages of the inventive ticket is the minimization of all fluid paths. Indeed, placement of a sample reservoir practically adjacent to a row of strips substantially reduces the distance which the sample solution travels between these components. Furthermore, by optionally providing each individual ticket with cleaning fluid or a solution reservoir, the system eliminates long cleaning-solution paths and obviates the need for a large-volume single cleaning fluid reservoir as well as for a waste basin. In the inventive system, as a testing stage is completed, the cleaning fluid is pumped out from the cleaning fluid reservoir to those fluid conveying parts which are not located on the ticket, and after the cleaning stage is complete, the contaminated solution returns back into the same reservoir. Note that upon completion of the test, the ticket, most likely, will not be needed.
Thus, having reduced the distance fluid travels and the number of components, the inventive fluidics system is simple and both space- and cost-efficient.
In accordance with a further aspect of the invention, the inventive system features a sample detection and fluid distribution component or unit detachably connectable to each of the tickets to provide controllable delivery and detection of agents and, also, delivery of cleaning solution or fluid after the detection test has been completed. The sample detection component includes a fluid transfer pump, a sample detector, solution and sample conveying elements as well as an air conduit to draw an air stream into the sample reservoir formed on the ticket.
Accordingly, the inventive system is a compact sample detection stage or system including two separate inventive units detachably coupled to one another. One of the unitsxe2x80x94the ticketxe2x80x94has sample collecting reservoir and multiple immunoassay strips, and the other unitxe2x80x94the sample detection and fluid distribution componentxe2x80x94has a means for distributing and detecting the sample.
Overall, the provision of the sample detection and fluid distribution component allows the user to provide a sequence of tests in a time-efficient manner substantially improving the known methodology of and the system for analyzing biological particles and microorganisms. The inventive system, in which the sample fluid reservoir and optionally the impinging nozzle and the cleaning solution reservoir are formed as a unit and attached to a cartridge provided with the immunoassay strips substantially minimizes the length of solution paths and simplifies the overall structure.
It is, therefore, an object of the invention to provide an integrated fluidics system for simplified analysis of aerosolized biological particles overcoming drawbacks of the known prior art systems.
A further object of the invention is to provide a self-contained sample or particle collection component or ticket having integrated therein a sample fluid reservoir.
Yet another aspect of the invention is to provide a sample detection and solution-distribution unit removably attachable to the ticket and providing the overall system with miniaturized fluidics contributing to a smooth and efficient process for conducting multiple tests.
Another object of the invention is to provide a controllable integrated sampling stage substantially minimizing mechanical operations.
Yet a further object of the invention is to provide a new and efficient method of controlling the integrated sampling stage.